1. Technological Field of the Invention
The present invention relates to a tool mounting device for a turning center that can suitably exchange rotating tools and turning tools to perform milling and cutting (turning).
2. Background Art
In a turning center, a mounting engagement unit for engaging a tapered shank provided to the base end of a tool is disposed on a main shaft that is rotatably mounted on a ram via a bearing unit. A clamp mechanism is disposed for clamping a clamping convexity of the tapered shank by retracting the drawbar and drawing/engaging the tapered shank to the mounting engagement unit to detachably/replaceably mount and fix the tool to the main shaft so as to allow the shaft to be clamped and released based on the reciprocating control of the drawbar. Tools are suitably attached and detached using the shared clamping mechanism, and rotating tools are rotatably clamped/fixed together with the main shaft. When turning tools are clamped/fixed, the tools are baffled and fixed together with the main shaft (fixed to the ram); and rotating tools and turning tools can thereby be suitably exchanged and mounted, and both milling and cutting can be carried out.
In such a turning center, when the clamp mechanism of the rotating tools and turning tools is configured so as to be shared as described above, the radial load on the turning tools is considerably greater than on the rotating tools, and the clamp force must therefore be increased. In order to do so, a hydraulic cylinder device with a large diameter for outputting a considerable drive force must be used, and there are configurations in which a hydraulic two-stage cylinder is used.
Therefore, since a hydraulic cylinder device is conventionally necessarily required, an oilless structure cannot be obtained and energy and resources cannot be saved.
Also, the bearing unit provided to the main shaft tends to be damaged in an arrangement in which the tapered shank is merely lifted with considerable force and drawn into close contact with the mounting engagement unit so as to be able to counter such a significant radial load, and a cutting force is imparted using a key.
Therefore, a turning tool is clamped/fixed by a method in which the tapered shank is not pressed into contact with the mounting engagement unit in order to form a gap, and a tapered portion is separately provided for the turning tool, or a method in which mechanical locking is ensured by curvic coupling or tapering based on hydraulic clamping or releasing.
When a tapered portion is separately provided for the turning tool, however, the tapered portion must be made relatively deep to offer taper support, and specially designed tools must therefore be used, which prevents tool magazine sharing and becomes an impediment to general purpose usage.
In the case of a mechanical lock, a dual-surface restraint can be implemented with a receiving portion and pressing of the mechanical lock. Specially designed tools are not required and existing turning tools can be securely fixed, but a mechanical lock structure must be provided to the distal end of the ram, the structure becomes complicated, and exchange operations cannot be carried out as easily.